title: Guanine binding to gold nanoparticles through nonbonding interactions.
abstract: Gold nanoparticles have been widely used as nanocarriers in gene delivery. However, the binding mechanism between gold nanoparticles and DNA bases remains a puzzle. We performed density functional theory calculations with and without dispersion correction on Au(N)( (N = 13, 55, or 147) nanoparticles in high-symmetry cuboctahedral structures to understand the mechanism of their binding with guanine at the under-coordinated sites. Our study verified that: (i) negative charges transfer from the inner area to the surface of a nanoparticle as a result of the surface quantum trapping effect; and (ii) the valence states shift up toward the Fermi level, and thereby participate more actively in the binding to guanine. These effects are more prominent in a smaller nanoparticle, which has a larger surface-to-volume ratio. Additional fragment orbital analysis revealed that: (i) electron donation from the lone-pair orbital of N to the unoccupied orbital of the Au cluster occurs in all complexes; (ii) π back-donation occurs from the polarized Au d(yz) orbital to the N p(y)-π* orbital when there is no Au···H-N hydrogen bond, and, (iii) depending on the configuration, Au···H-N hydrogen bonding can also exist, to which the Au occupied orbital and the H-N unoccupied orbital contribute.
authors.affiliation: Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore637371. hirao@ntu.edu.sg.
authors.forename: Xi
authors.initials: X
authors.lastname: Zhang
authors.forename: Chang Q
authors.initials: CQ
authors.lastname: Sun
authors.forename: Hajime
authors.initials: H
authors.lastname: Hirao
mesh_terms: D006046:Gold / Q000737:chemistry*; D006147:Guanine / Q000737:chemistry*; D006860:Hydrogen Bonding; D053768:Metal Nanoparticles / Q000737:chemistry*; D011789:Quantum Theory; D013816:Thermodynamics
chemical_list: D006147:Guanine; D006046:Gold